An electronic device may enact a power-management scheme to reduce power consumption, limit heat dissipation, extend battery life, etc. One aspect of the power management scheme may target so-called ‘leakage currents’ in the device-relatively small currents that flow through a component of the device when that component is idle. To this end, the device may include a power-management unit (PMU) configured to detect an idle condition of one or more device components. After the idle condition is detected, the logic state of the idle component may be saved, and the supply voltage to that component disconnected. In that manner, the leakage current that would otherwise be drawn through the component is greatly reduced. After a period of time, the PMU may detect a request to resume operation of the unpowered component. At that point, the supply voltage to the component is restored, and the logic state of the component is recovered.
The power-management scheme summarized above is more useful for some devices and usage scenarios than for others. The feature that limits its utility is the need to save the logic state of the idle component every time the idle condition is detected, and to recover the logic state every time the component is returned to operation. In general, each save and recovery operation requires time, processing power, and energy. Accordingly, the above scheme is most applicable in scenarios in which the idle condition is relatively infrequent and relatively long-lived. If more frequent save and restore operations are required, the overall performance of the device may suffer, and the potential power savings may be eroded.